Under the self-employed CIS4 system you pay 20% tax weekly stopped by your boss You need to do a tax return and pay your national insurance contributions at the end of the year 9% of profit Many migrants do not pay this bill ,choosing to abscond ,uk resident citizens affectively pay 29% migrant labour 20%. The revenue could prevent this by increasing the weekly contributions to 29% . Another example of uk labour being disadvantaged by migrant labour - See more at:
http://www.dover.uk.com/forums/dover-forum/uk-labour-tax-disadvantage#sthash.fyT2P6IF.dpuf